Fuel burner control system



June 5, 1945. J. M. WILSON 2,377,535

FUEL BURNER CONTROL SYSTEM Filed March 5, 1942 INVENTOR 1301mm M. Wilsom ATTORNEY Patented June 5, 1945 FUEL BURNER CONTROL SYSTEM John M. Wilson, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application March 5, 1942, Serial No. 433,494

20 Claims.

This invention is directed broadly to an auto-' matic control system for a fluid fuel burner, and more specifically to a control system in which an electric motor controls the variou timing sequences in automatically starting and stopping the operation of the fuel burner.

One of the main objects of the present invention is to provide a system of the above type in which a control motor'is energized upon a demand for burner operation to simultaneously energize the ignition device and cause a delivery of fuel to the burner, to open a safety switch in the event that combustion is not established after said motor has been operating for a predetermined period of time, but if combustion is established before the time has elapsed to continue operating until it reaches a running position in which it remains until the demand for burner operation has been satisfied at which time it closes a return switch to cause it to return to its original or starting position, at the same time shutting down the burner.

A further object in the invention is to cause the control motor to close the return switch at the same time that the safety switch is opened so that the control motor will then return to its. original position while the safety switch remains open.

A further object of the invention is to operate the automatic control system by means of an electric motor having a stator, and rotor, the stator assuming a first position when the motor is deenergized and being movable to a second position when the motor is energized due to a reaction between the rotor and the stator. The

' system is further arranged so that each time the control motor is deenergized it operates to close the return switch for the purpose of returning the motor and the control to their origi nal or starting position, it being understood that the control motor will not close this return switch when itis in its starting position.

A further object of the invention is to provide a simplified motor operated burner control system which has all of the necessary features of safety, these features of safety being provided by the control motor thus eliminating the necessity for any electro magnetic relays. 1

These and other objects of the invention will readily become apparent as the following speciflcation is read in the light ofthe accompanying drawing in which Figure 1 illustrates a control circuit incorporating the various features of my invention,

vFigure 2 is a diagrammatic representation of my control motor and a control unit in the form of a plurality in cams which are operated thereby to perform various control functions, and

Figure 3 is a view similar to Figure 2 showing the cams in a different operative position.

Referring now to the drawing the reference numeral l0 indicates generally an electric motor having a stator H and a rotor l2. This motor is of the unidirectional type and has a constantly energized main winding l3 and a shading winding it. As long as the circuit to the shad ing winding I4 is open, the motor is stationary, but as soon as the circuit is closed thus short circuiting the winding H, the motor will start to operate. Motors of this type are old and well known in the art.

The stator II is rotatably mounted on th same axis M as is the rotor l2, the stator being biased into engagement with a stop l5 by means of the biasing spring l6, shown diagrammatically in Figure 2. When the shading winding I4 is energized a starting torque is developed and the reaction between the rotor 12 and the stator l I causes the stator to rotate in a counter-clockwise .directio nand engage the stop 11. The stator I I will remain in this position until the winding I4 is deenergized at which time it will return to its originalposition and engage the stop J5 under the influence of the biasing spring l6.

1 The rotor I2 is connected through the reduction gears I 9 to a rotatable shaft 20 indicated in the dotted lines in the drawing. Cams 2|, 22, 23 and 24 are mounted on the shaft 20 for rotation thereby.- The shaft 20 and the cams form a control unit which may be designated by the reference numeral 25. An operating member 26 is freely pivoted on the shaft 20 and is adapted to be moved back and forth by the stator I l as it moves between its two stops I5 and H. For the purpose of simplifying the drawing the operating member 26 has been shown as connected to the stator H by means of a link 21 but it will readily be appreciated that in actual practice the shaft 20 extends parallel to or concentric with the axis l4 about which the rotor l2 rotates and that therefore the operating member 26 may be directly connected to the stator II. In any event it will be clear from the drawing that the operating member 26 is moved back and forth as the motor shading winding I4 is energized and deenergized causing the stator H to move back and forth between the two stops I5 and H.

The cam 2| is adapted to control the two electric switches 28 and 29 which are shown as comprising a pair of resilient blades 30 and 32 which are biased to their straight line position and a resilient blade 3| which is located between these two blades and biased upwardly, as shown in Figure 2. The blade 3| has an extension carrying an insulating member 33 which rides on the surface of the cam 2|. The cam 21 has a low portion 34 which permits the blade 3| to move upwardly under the influence of its own bias both opening the switch 29 and closing the switch 28. As the cam 2| rotates in a clockwise direction the insulating member 88 will engage the intermediate portion of the cam surface 88 and force the blade 8| downwardly in which position it will cause closure of the switch 28, but will not be moved down far enough to open the switch 28. By further rotation of the cam 2| the insulating member 88 will engage the high portion 88 thereof and force the blade 8| downwardly to a position where it opens the switch 28 while maintaining the switch 28 in closed'position.

The cam 22 is adapted to control the switch 88 which is shown as comprising a resilient contact blade 38 biased to its horizontal position and a second resilient blade 48 biased upwardly as shown in Figure 2 and carrying at its free end an insulating member 4| which cooperates with the surface of the cam 22. When the insulating member 4| engages the low surface of the cam 22 as shown in Figure 2 the switch 38 is open but when the cam 22 rotates to a position where the high part of the cam engaged insulating member 4| the switch 88 is closed as shown in Figure 3.

The cam 28 controls the switch 48 which is essentially similar to the switch 88, being composed of a resilient blade 44 which is biased to horizontal position and a resilient blade 48 which is biased upwardly as shown in Figure 3, the blade 45 carrying at its free end an insulating member 46 which cooperates with the surface of the cam 23. When the high surface of the cam 28 engages the insulating member 48 the switch 48 is closed as shown in Figure 2 but when the low portion of the cam 28 engages the insulating member 48 the switch 48 is open as shown in Figure 3.

The cam 24 operating in conjunction with the operating member 28 is adapted to control the return switch 48 and a pair of safety switches 48 and 88. Considering. first the return switch 48, this switch is shown as comprising a pair of resilient contact blades 8| and 82 which are biased to open position, but which may be moved to closed position by means of the lever 88 which is shown as being pivoted at 84. When once closed the switch 48 is latched in closed position by means of the latching surface 88 on the latch member 88 which is pivoted at 81 and biased to its latched position by means of the biasing spring 88. The operating link 88 is pivotally connected I at one end to the lever 88 for transmitting motion from the operating member 28 to the lever 88 for movingthe return switch 48 to closed position. When the latch 88 and link 88 are in their upper position as shown in Figure 3 the link 88 is so positioned that when the control motor I8 is deenerglzed and the stator |I returns to its position in engagement with the stop |8 the operating member 28 will be rotated to force the link 88 to the left as seen in the drawing, resulting in the closure of the return switch 48 and the latching thereof on the latching surface 88 on the latch member 88. When the latch member 88 and the link 88 are in their lower position as seen in Figure 2 the link 88 is out of the path of movement of the operating member 28 so that even though the control motor is deenergized and the operating member rotates in a clockwise direction it will have no effect upon the return switch 48. The latch member 88 is controlled in its position by means' of a pin or roller 8| which rides upon the surface of the cam 24. As long as this roller 8| is in engagement with the high surface 82 of the cam 24 as shown in Figure 2, it positions the link 88 so that it cannot be engaged by the operating member 28, but when this roller engages any part of the remaining portion of the cam surface the link 88 is positioned as shown in Figure 3, at which time the deenergization of the control motor l8 will cause the operating member 28 to close and latch the return switch 48.

The safety switch 88 is shown as comprising a pair of resilient contact blades 84 and 88 which are biased to closed position as shown. The safety switch 48 is formed by a resilient contact blade 88 which is biased to its horizontal position and a second contact blade 81 which is biased downwardly to open circuit position but which is normally held in circuit closed position by means of the latch 88 which engages the free end of the blade 81. The latch 88 is pivoted at 88 and when it rotates in a counter-clockwise direction it releases the free end of the blade 81 which moves downwardly to open the switch 48 and which through the pin 18 opens the switch 88. It will therefore be seen that the removal of latch 88 from engagement with blade 81 causes the opening of both the safety switches 48 and 88.

The latch 88 is adapted to be operated by means of a trip member 12 which is freely pivoted at I8 to one end of a lever I4. The lever I4 is in turn pivoted at 18 and at its other end carries a roller I8 which cooperates with the surface of the cam 24. A biasing spring Il holds the lever I4 in such a position that the roller I8 is always in engagement with the cam 24. When the roller- 18 engages the low portion ll of the cam 24 the lever I4 rotates in a counter-clockwise direction about its pivot I8 and raises the entire trip member I2 to the position shown in dotted lines in Figure 2 of the drawing. With the trip member in this position it can be seen that when the control motor I8 is deenergized and the operating member 28 rotates in a clockwise direction it will engage the left hand end of the trip member I2 and cause it to rotate in a counter-clockwise direction about its pivot I8 and cause the cam surface 18 to engage the pin I8 thereby rotating the latch 88 in a counter-clockwise direction and releasing the contact blade 81 which opens both the switches 48 and 88. When the roller I8 on the lever I4 is in engagement with any other portion of the cam surface except the low portion 11 the trip member I2 will be lowered to such a position that it is out of the path of movement of the operating member 28. Thereforerthe only time during which deenergiaztion of the control motor can operate to open the safety switches 48 and 88 is when the roller I8 is in engagement with the low portion of the cam surface 11.

The cam 24 carriesan abutment 88 which is adapted to pass freely beneath the trip member I2 and link but which is adapted to abut the end 8| of the lever 88 as indicated in Figure 8. This causes the control motor II to stall until the lever 88 is removed from engagement with the abutment 88 thereby permitting continued rotation of the control motor.

Figure 1 illustrates a circuit diagram of a control system utilizing the control motor and control unit shown in Figures 2 and 3. Any one of a number of various standard condition responsive devices may be utilized for sensing a demand for burner operation and thus initiate operation -of the control system as a whole, but for the purposes of illustration the control sytem has been .tact 89 and then at a slightly lower temperature are old and well known in the art.

The switches 28, 29, 38, 43, 48. 49, and 58 which are operated by the various cams in Figures 2 and 3, have been given the same reference numerals in Figure 1. The switch arm 98 and stationary contact 99 correspond to the same elements in Figures 2 and 3. This switch arm 98 is adapted to be operated by the stator II as the control motor is energized and deenergized. The switch arm is so arranged that when the control motor is deenergized and the stator is up against the stop Ilthe switch arm 98 is in open position whereas when the control motor is energized and the stator is against the stop I! the switch arm 98 is moved into engagement with the stationar contact 99.

Although this control system could be utilized for the control of various types of fuel burners, for the purposes of illustration, it has been shown in connection with an oil burner, The reference numeral I88 therefore indicates the usual oil burner motor and the reference numeral I8I indicates an ignition device for igniting the fuel delivered to the burner by the burner motor I88.

The electrical power for operating the system is supplied by the two line wires I82 and I83 to which the main winding I3 of the control motor I I is constantly connected through the conductors I84 and I85. As explained above the rotation of the control motor I8 is controlled entirely by short circuiting the shading winding [4.

Operation If the burner motor I88 and ignition device I8I are deenergized the temperature in the room in which the room thermostat 85 is located willbegin to fall and first cause the resilient blade 81 to engage the stationary contact 89. This will not affect the system in any way due to the fact that the switch 88, 98 is open and the switch 98,

, 99 open. The temperature in the room will therefore continue to decrease until the bimetallic element 88 causes the contact 88 to moveinto engagement with the stationary contact 98. This completes a starting circuit for short circuiting bustion responsive switch arm 93. cold contact 94 and conductors I I3 and II 4 back to the other side of the mafia; winding :4. This'will result in the energization of the control motor I8 and the resultant reaction between the stator II and rotor I2 will cause the stator to rotate from engagement with the stop I6 into engagement with the stop IT. This is the condition which is shown in Figures 1 and 2. It will be noted that at the time the control motor I8 is originally energized the control unit 25 is in its starting position in which the insulating element 33 engages the low portion 34 of the cam 2| thereby resulting in the closure or the switch 28- and the opening of the switch 29. The motor control switch 38 is in open position and the ignition switch 43' is closed.

P It will be noted however, that the motor control switch 38 is in series with the ignition device I8I so that both the burner motor I88 and the ignition device I 8 I are vdeenergized at this time. The latch member 38 is in its tripped position due to the fact that the roller 8I is engaging the high portion 62 of the cam 24. Therefore the return switch 48 is open. The trip member I2 is in its lower position due to the fact that the roller "I3 on the lever I4 is not engaging the low portion 11- of the cam 24. The contact blade8l is latched on the latch 88 and therefore the safety switches 49 and 58 are in the closed position.

As pointed out above, the switch arm 98 engages its stationary contact 99 as soon as the control motor I8 is energized and the stator rotates into engagement with-the stop II. Closure of this switch establishes a holding circuit for the shading winding I4 which is independent of the switch blade 88 and the contact 98. This circuit extends from one side of. the shading winding' through conductor I81, safety switch 49, conductor I88, contact 89, flexible switch blade 81, 131-. metallic element 88, conductor H5, switch arm 98, stationary contact 99, conductors I I8, II 8 and I I I, switch 28, conductor I I2, combustion responsive switch arm 93, cold contact 94 and conductors II 3 and H4 back to the other side of the shading winding I4. Therefore after the control motor I8 has once been energized the switch blade 88 may move out of engagement with the stationary contact 98 without affecting the energization of the control motor I8.

Operation of the control motor I8 will cause the cams H, 22, 23 and 24 to rotate in a clockwise direction. The first operation performed by the cams is that the cam 22 causes closure of the motor control switch 38. This causes energize,- tion of the burner motor I88 by means of a circuit extending from the line wire I82 through conductor II8, safety switch 58, conductor II 9, burner motor switch 38, conductors I28 and HI, burner motor I88 and conductors I22 and I23 back to the other line wire I83.' The ignition device I8I will be simultaneously energized by a circuit extending from the line wire I02 through conductor 8, safety switch 58, conductor II9, burner motor switch 38, conductors I28 and I24. ignition switch 43, conductor I25, ignition device MI, and conductors I28 and I23 back to the other line wire I83. Therefore th burner motor and the ignition device will be energized substantially immediately upon the energization of the control motor I8.

At substantally the same time the insulating member 33 will ride up on the end of the intermediate portion 35 of the surface of the cam 2| which will cause the blade 3| to move downwardly and close the switch 29 while maintaining switch 28 is-closed. This establishes a holding circuit for the shading winding I4 which is independent of the combustion responsive switch -arm 88. This holding circuit extends from one side of the shading winding I4 through conductor lcl, safety switch 48, conductor I08, contact 88, .switch blade 81, bimetallic element 88, conductor I I5, switch arm 88, contact 88, conductors iii, 8 and Ill, switches 28 and I! in series energization of the ignition device, the insulating member 88 rises upon the high side 88 of the cam 2| thereby opening the switch 28 while maintaining the switch 28in the closed position. It will be recalled that-the switch 28 was in the original starting circuit for the control motor I and also in the holding circuit which was closed after operation in the control motor II hasstarted.

If combustion has not been established at this time the combustion responsiv switch arm 83 will remain in engagement with the cold contact 84 and the control motor II will therefore become deenergized. It will be noted that when the control unit 28 has been rotated far enough to close the switch 29 and then open the switch 28 that the high point 82 of the cam 24 will have passed from beneath the roller 8| on the latch member 88 and therefore this member will have positioned the link '88 up into the path of movement of the control member 28. Therefore, when the control motor I0 is deenergized at this time and its stator rotates-back into engagement with the stop 88 the resultant clockwise rotation of the control member 28 will cause it to strike the link 88 and move the lever 88 to the left thereby latching the return switch 48 in the closed position on the latching surface 88 of the latched member 88.

Also at the time the switch 28 is opened by the cam 2| the roller I8 on the lever I4 will be in the low portion I1 and the cam 24 which means that the tripping member I2 will be in its upper position at which time it will also be in the path of movement of the operating member 26. Therefore, when the control motor is deenergized at this time the resultant movement of the operating member" will cause a counter-clockwise rotation of the tripping member 12 which win then engage the pin I8 on the latch 88 and move this i latch from engagement with the resilient blade 81 thereby permitting it to open both safety switches 48 and 88.

f Thus, if combustion is not established at the end of the trial ignition period when the switch 28 is opened by the cam 2| then both of the safety switches 48 and 88 are latched in open position and'the return switch 48 is latched in the closed position. Opening of the safety switch 88 immediately deenergizes the burner motor, the ignition device III having previously been deencrgized by the opening of the ignition switch 48. Opening of the safety switch 48 opens the thermostat circuit which prevents the closure of any circuit through the shading winding I4 by the thermostat until the two safety switches have been manually reclosed. The closing of the return switch 48 establishes a circuit through the shading 'winding I4 which extends from one side of this winding through conductor I88, return s,s17,sss

switch 48, and conductor "I back to the other side of the shading winding l4. This therefore immediately reenergizes the control motor III which continues rotating until the high portion 82 of the cam 24 enga es the roller 8| on the latch lever 88 and moves this lever to its tripped position resulting in the opening of the return switch 48 and the subsequent deenergization-of the control motor I8. At this time however, it will be noted that the link 88 has been moved out of the patch of movement of the operating member 28 as has been the tripping member I2. The control motor I8 therefore remains deenergizcd and cannot be reenergized until the safety switch 48 is manually reset. Also, the burner motor I00 and the ignition device Ill remain deenergized until the safety switch 80 has been manually reset. When the trouble which resulted in the failure of the burner to properly ignite has been remedied and the two switches 48 and 88 have been manually reset, the control motor III will again be energized through the room thermostat 88 and the circuits described above will again be closed to cause the system to attempt to start.

Assume now that the control motor III has been reenergized and that the control unit 28 ha first closed the burner motcr switch 38 and then opened the ignition switch 48 and that it has also closed the switch 28 for establishing the holding circuit for the control motor I 8 and then has opened the switch 28 in the starting and holding circuits. If combustion has been established at this time then the combustion responsive switch arm 83 is in engagement with the hot contact 88. The shading winding I4 then remains energized following the opening of the switch 28 by means of a circuit extending from one side of the shading winding I4 through conductor IIII, safety switch 48, conductor I88, contact 88, switch blade 81, bimetallic element 88, conductor H8, switch arm 88, contact 88, conductors H8, H8 and I82, hot contact 88, combustion responsive switch arm 83, conductor H2, switch 28 and conductor I28 and H4 back to the other side of the shading winding I4.

its stationary contact 88 and as long as the combustion responsive switch arm 88 is in engagement with its hot contact 88.

If either of these switches are opened however, the control motor I8 is deenergized and as the link 88 is in its upper position at this time, the control member 28 will close and latch the return switch 48. The tripping member I2 at this time will be in its lower position due to the fact that the roller I8 will not be in the low portion II of the cam 24. Therefore, the deenergization of the control motor at this time will not operate to unlatch the resilient blade 81 and the safety switches 48 and 88 will remain closed. The only time that the deenergization of the control motor is operative to cause the operating member to unlatch the two safety switches 48 and 88 is at the time the switch 28 is opened by the cam 2|, at which time the roller 18 is in the low'portion I! of the cam 24 and the tripping member I2 is in its raised position in which it is in the path of movement of the operating member 28.

The return switch as being in its closed position the control motor It will operate to rotate the control unit until the high portion 62 of the cam ll operates to lower the latching member 56 and release the return switch 48 to move to its open position. This occurs in the starting position of the control unti as illustrated in Figure latched closed with the result that the control motor will continue to operate until it returns to its starting position, at which time, if the room thermostat is stlll'calling for heat, the control will go through its normal starting cycle. It will be noted further that as the control motor rotates the control unit 25 from its running position to its starting position it provides for a sufllcient time delay to clear the combustion chamber of all combustible fumes which might result in an explosion when the ignition device is reenergized. Therefore, even though the burner motor is reenergized when the, power comes on following a power failure it will be deenergized by opening the motor switch 38 and then the control motor will provide for'a scavenger period before the ignition device can again be reenergized when the system attempts to start.

Many changes and modifications of this inven tion will undoubtedly occur to those who are skilled in the art and I therefore wish it to be understood that I intend to be limited by the said control motor after a predetermined time for opening said motor operated switch in said first circuit, means responsive to the-opening 01' said first circuit for opening said safety switch in the event that said hot combustion switch is not closed when said motor operated switch is opened, means operated by the continued operation of said control motor, in the event that said safety switch is not opened, for terminating ignition, and means operative to stop said control motor in a position in which said electrical means is delivering fuel and said ignition means inoperative.

3. In a motor operated fuel burner control system, a control motor, hot and cold combustion switches, a motor operated switch, a condition responsive switch, a first circuit controlling the energization of said control motor, said circuit means including said condition responsive switch,

, cold combustion switch and motor operated scope of the appended claims and not by the control of said fuel delivery means, a circuit ineluding said hot combustion switch for maintaining energization of said control motor, means operated by said control motor after amredetermined time for opening, said motor operated switch in said first circuit, and means responsive to the opening of said first circuit for open said safety switch in the event that said hot combustion switch is not closed when said motor operated switch is opened;

'2: In a motor operated fuel burner control system, a control motor, hot and cold combustion switches, a motor operated switch, a conditionresponsive switch, a first circuit controlling the energization of said control motor, said circuit means including said condition responsive switch, cold combustion switch and motor operated switch, electrical fuel delivery means and ignition means rendered operative by said control motor upon energization thereof, a normally closed safety. switch in control of said fuel delivery means and ignition means, a circuit including said hot combustion switch for maintaining energization of said control motor, means operated by switch, electrical fuel delivery means rendered operative by said control motor upon energization thereof, a normally closed safety switch in control of said fuel delivery means, a second motor operated switch closed by said control motor upon energization thereof, a pair of circuits either of which can maintain energization of said control motor independently of said cold combustion switch, the first of said pair of circuits including the first and second motor operated switches in series, the second of said pair 4. In a motor operated fuel burner control sys-' tem, a control motor, a condition responsive switch for controlling the energization of said control motor, a fuel delivery device, means operated by said control motor upon energization thereof for rendering said fuel delivery device operative to deliver fuel to a burner, a normally closed safety switch, means controlled by said motor for opening said safety switch a predetermined time after said fuel delivery means has been rendered operative, th opening of said safety switch rendering said fuel delivery means inoperative, means including a combustion responsive means for preventing the opening 'of said safety switch in the event that combustion is established first, means operated by said control motor for thereafter stopping said control motor in a position to maintain said fuel delivery means operative, and means including a return switch for energizing said control motor upon opening of said condition-responsive switch for returning said motor to a position where it renders said fuel delivery means inoperative. v

5. In a motor operated fuel burner control, a control motor, a control unit operated there y,

fuel control means operated by said control unit for controlling the flow of fuel to a burner, said control unit having a starting position in which no fuel is flowing to the burner, a control circuit including a condition responsive switch for energizing said control motor to cause it to'move said control unit toward a running position,

means operated by saidmotor for stopping said control means being operated by said control unit as it leaves its starting position for causing a fiow of fuel and maintaining said fiow as it continues to its running position, a return switch for said control motor, circuit responsive means for closing said return switch when said control circuit is deenergized for any reason for causing operation of said control motor, said fuel control means terminating said fuel flow as said control unit is moved by said control motor out of its running position toward its starting position, and means operated by said control unit for openin said return switch when said control unit has reached its starting position.

6. In a motor operated fuel burner control, a control motor, a control unit. operated thereby, fuel control means operated by said control unit for controlling the flow of fuel to a burner, means for igniting said fuel, said control unit having a starting position in which both said fuel control means and igniting means are inoperative, a control circuit including a condition responsive switch for energizing said control motor to cause it to move-said control unit to a running position, means operated by said control unit as it moves out of its starting position for operatin said fuel control means to cause delivery of fuel 1 to the burner and for energizing said igniting means and then deenergizing said igniting means before said control unit reaches its running position, means operated by said control unit for stopping said motor when said control unit reaches its running position, a return switch for said control motor, circuit responsive means for closing said return switch when said control circuit is deenergized for any reason for causing operation of said control motor, said fuel control means terminating said fuel flow as said control unit is moved by said control motor out of its 4o tor, said state;- being rotatable coaxinlly with running position toward its starting position, and means operated by said control unit for opening said return switch when said control unit has reached its starting position.

'7. In a motor operated fuel burner control, a

control motor, a control unit operated thereby;

an electrical device which, when energized, causes the delivery of fuel to a burner, a first switch for energizing said device actuated by said control unit, said control unit having a starting position in which said first switch is open, a normally closed safety switch in control of said fuel delivery device, a control circuit including a condition responsive switch for energizing said control motor to move said control unit toward a running position, means operated by said control unit for closing said first switch as said control unit leaves its starting position, means positioned bysaid control unit when it reaches an intermediate position for opening said safety switch, means responsive to the establishment ofcombustion at said burner for preventing such opening-of the safety switch if combustion is established first,

' means operated by said control unit for stopping said control motor when said control unit reaches its running position, a return switch for said con- 66 trol motor, circuit responsive means for closing said return switch when said control circuit is deenergized for any reason for causing said control motor to move said control unit to its start- .ing position, said control unit opening said first switch when it moves out of its running position,

b and means operated by said control unit for opening said return switch when said control unit has i reached its starting position. I 8.- In a motor operated fuel burner control system, a. control motor having a rotor and a stay tor, said stator being rotatable coaxially with said rotor between first and second positions, means biasing said stator to its first position, a control unit, reduction gearing through which said control unit may be operated by said rotor, an electrical device which, when energized, causes the delivery of fuel to a burner, a first switch in control of said last named device erated by saidcontrol unit, said control unit having a starting position in which said first switch is open, an operating circuit for said control motor including a condition responsive switch, the reaction between the rotor and stator upon the establishment of said operating circuit causing said rotor to rotate in one direction and said stator to rotate in the opposite direction against its bias to its second position, said control unit being moved by said rotor from its starting position to a running position, said control unit closing said first switch as it movesfromdts starting position, a fixed stop, means associated with said control unit engaging said med-stop to stall said control motor, a return switch for said control motor, means operated by said:- tor as it returns to its first position under the influence of its bias when said operating circuitis broken causing removal of said stop and closure of said return switch, circuit means established by said return switch for energizing said control motor to move said control unit to its starting position, said control unit opening said first switch as it moves from its running position. and means operated by said control unit for opening said return switch thereby dccnergizing said control motorv when said control motor reaches its starting position. I

9. Inc motor operated fuel burner control system, a control motor having a rotor and a stacontrol unit, a safety switch in control of said electrical device, said control unit havin: a starting position in which saidflrst switch is open and said second switch closed, a first operating cir- I cuit for said control motor including a condition responsive switch and said second switch, the reaction between the rotor and stator upon the establishment of said operating circuit causing said rotor to rotate in one direction and said stator to rotate in the opposite direction against its bias to its second position, said control unit being moved by said rotor-from its starting position toward a running position. said control unit closing said first switch as it moves from its switch as it moves to an intermediate politlm to interrupt said first operating circuit for the control motor, interruption of said first operating circuit causing said stator toreturn to its first podtion under the influence of its bins if said control motor is deenergind at this time means operated by said stator for opening said safety '1: said control motor is sooner-shod whm" me control unit' n in its intermediate a secondoperating circuit for said control motor including a closed hot combustion switch. sold last named circuit preventing decnorgi-Mlon of an electrical-device which, whenenergized, causes the delivery of fuel to a burner, a first switch in control of said last named device operated by said control unit, a second switch operated by said control unit, a safety switch in control of K as it moves from its starting position, a fixed stop,

means associated with said control unit engaging said fixed stop to stall said control motor, a return switch for said control motor, means operated by said stator as it returns to its first position under said electrical device, said control unit having a starting position in which said first switch is open and said second switch closed, a first operating circuit for said control motor including a condition responsive switch and said second switch, the reaction between the rotor and stator upon the establishment of said operating circuit causing said rotor to rotate in one direction and said stator to rotate in the opposite direction against its bias to-its second position, said control unit being moved by said rotor from its starting position toward a running position, said control unit closing said first switch as it moves from its starting position and then opening said second switch as it moves to an intermediate position to interrupt said first operating circuit for the control motor, interruption of said first operating circuit causing said stator to return to its first position under the influence of its bias if said control motor is deenergized at this time, means operated by said stator for opening said safety if said control motor is deenergized when said control unit is in its intermediate position, a second operating circuit for said control motor including a closed hot combustion switch, said last named circuit preventing deenergization of said control motor at the intermediate position of said control unit provided combustion is established before said control unit reaches its said intermediate position, a fixed stop, means associated with said control unit engaging said fixed stop to stall said motorwhen said control unit reaches its running position, a return. switch, said stator closing said return switch when said control motor is deenergized and also removing said fixed stop whereby said control motor is reenergized to return said control unit to its starting position, and means operated by said control unit for opening said return switch when said control unit reaches its starting position. I

11. Ina motor operated fuel burner control system, a control'motor having a rotor and a stator, said stator being rotatablecoaxially with said rotor between first and second positions, means biasing said stator to its first position, a control unit, reduction gearing through which said control unit may be operated by said rotor, an electrical device which, when energized, causes the delivery of fuel to a burner, a first switch in control of said last named device operated by said control unit, said control unit having a starting position in which said first switch is open, an operating circuit for said control motor'including a condition responsive switch; the reaction bethe influence of its bias when said operating circuit is broken causing removal of said stop and closure of said return switch, circuit means established by said return switch for energizing said control motor to move said control unit to its starting position, said control unit opening said first switch as it moves from its running position, means operated by said control unit for opening said return switch thereby deenergizing said control motor when said control motor reaches its starting position, and means preventing said stator from reclosing said return switch when said control motor is deenergized upon re turning said control unit to its starting position.

'12. In a motor operated fuel burner control system, a control motor having a rotor and a stator, said stator being rotatable coaxially with said rotor between first and second positions, means biasing said stator to its first position, a control unit, reduction gearing through which said control unit may be operated by said rotor, an electrical device which, when energized, causes the delivery of fuel to a burner, a first switch in control of said last named device operated by said control unit, a second switch operated by said control unit, a safety switch in control of said electrical device, said control unit having a starting position in which said first switch is open and said second switch closed, a first operating circuit for said control motor including a condition responsive switch and said second switch, the reaction between the rotor and stator upon establishment of said operating circuit causing said rotor to rotate in one direction and said stator to rotate in the opposite direction against its bias to its second position, said control unit being moved by said rotor from its starting position toward a running position, said control unit clos ing said first switch as it moves from its starting position and then opening said second switch as it moves to an intermediate position to interrupt said first operating circuit for the control motor, interruption of said first operating circuit causing said stator to return to its first position under the influence of its bias if said control motor is deenergized at this time, means operated by said stator for opening said safety if said control motor is deenergized when said control unit is in its in termediate position, a second operating circuit for said control motor including a closed hot combustion switch, said last named circuit preventing deenergization of said control motor at the intermediate position of said control unit provided combustion is established before said control unit reaches its said intermediate position, means for stopping said control motorv when it reaches its running position, and a return switch for said control motor, said stator closing said return switch if said control motor is deenergized when said control unit is in its intermediate position whereby said control unit will be returned to its starting'position while said safety switch remains open.

13. In a motor operated fuel burner control system, a control motor having a rotor and a stator, said stator being rotatable coaxially with said rotor between first and second positions, means biasing said stator to its first position, a control unit, reduction gearing through which said control unit may be operated by said rotor, an electrical device which, when energized, causes the delivery of fuel to a burner, a first switch in control of said last named device operated by said control unit, a second switch operated by said control unit, a safety switch in control of said electrical device, said control unit having a starting position in which said first switch is open and said second switch closed, a first operatin circuit for said control motor including a condition responsive switch and said second switch, the reaction between the rotor and stator upon the establishment of said operating circuit causing said rotor to rotate in one direction and said stator to rotate in the opposite direction against its bias to its second position, said control unit being moved by said rotor from its starting position toward a running position, said control unit closing said first switch as it moves from its starting position and then opening said second switch as it moves to an intermediate position to interrupt said first operating circuit for the control motor, interruption of said first operating circuit causing said stator to return to its first position under the influence of its bias if said control motor is deenergized at this time, means operated by said stator for opening said safety if said control motor is deenergized when said control unit is in its intermediate position, a second operating circuit for said control motor including a closed hot combustion switch, said last named circuit preventing deenergirntion of said controlmotor at the intermediate position of said control unit provided combustion is established before said control unit reaches its said intermediate position,- means for stopping said control motor when it reaches its running position, a return switch for said control motor, said stator closing said return switch if said control motor is deenergized when said control unit is in itslintermediate position whereby said control unit will be returned to its starting position while said safety switch remains open, and means preventing reclosure of said first operating circuit for said control motor when said control unit has returned to its starting position until said safety switch has been reclosed.

14.111 a motor operated fuel burner control, a control motor, a control unit operated thereby, an electrical device which, when energized, causes the delivery of fuel to a burner, igniting means for the fuel, an ignition switch in control of said igniting means, a first switch in control of both said igniting means and fuel delivery device, both said switches being actuated by said control unit, a normally closed safety switch in control of said fuel delivery device and igniting meana said control unit having a starting position in which said first switch is open, a control circuit including a condition responsive switch for energizing said control motor to cause it to move said control unit towards a running position, said control unit closing said first switch as it moves from its starting position and then later open ng said ignition switch, said ignition switch having been closed by said control unit prior to closure of said first switch, means positioned by said control unit as it reaches an intermediate position for opening said safety switch, means responsive to the establishment of combustion at the burner for preventing such action if-combustion is established first, means operated by said control unit for stopping said control motor when said control unit reaches its running position, a return switch for said control motor, circuit responsive means for closing said return switch when said control circuit is deenerglzed for any reason for causing said control motor to move said control unit to its starting position, said control unit opening said first switch when it moves out of its running position, and means operated by said control unit for opening said return switch when said control unit has reached its starting position.

15. In a motor operated fuel burner control system, a control motor having a rotor and a stator, said stator being rotatable coaxially with said rotor between first and second positions, means biasing said stator to its first position, a control unit, reduction gearing through which said control unit may be operated by said rotor, an electrical device which, when energized, causes the delivery of fuel to a burner, a first switch in control of said last named device operated by said control unit, a second switch operated by said control unit, a safety switch in control of said electrical device, said control unit having a starting position in which said first switch is open and said second switch closed, a first operating circuit for said control motor including a condition responsive switch and said second switch, the reaction between the rotor and stator upon the establishment of said operating circuit causing said rotor to rotate in one direction and said stator to rotate in the opposite direction against its bias to its second position, said control unit being moved by said rotor from its starting position toward a running position, said controlunit closing said first switch as it moves from its starting position and then opening said second switch as it moves to an intermediate position to interrupt said first operating circuit for the control motor, operating means adapted to be moved in a certain path by said stator as it moves between its first and second positions, an actuator for said safety switch controlled by said control unit, said control unit normally keeping said actuator out of the path of movement of said operating means but moving said actuator into said path as said control unit reaches its intermediate position, interruption of said first operating circuit causing said stator to return to its first position under the influence of its bias if the control motor is deenergized at this time whereby said operating means engages said actuator and opens said safety switch, a second operating circuit for said control motor includin a closed hot combustion switch, said last named circuit preventing deenergizatlon of said control motor at the intermediate position of said control unit provided combustion is established before said control unit reaches its said intermediate position, and means for stopping'said control motor when it reaches its running position. v

16. In a'motor operated fuel burner control system, a control motor having a rotor and a stator, said stator being rotatable coaxially with said rotor between first and second positions, means biasing said stator to its first position, a control unit, reduction gearing through which said control unit may be operated by said rotor, an electrical device which, when energized, causes the delivery of fuel to a burner, a first switch in control of said last named device operated by said control unit, a second switch operated by said control unit, a safety switch in control of said electrical device, said control unit having a starting position in which said first switch is open and said second switch closed, a first operating circuit for said control motor including a condition responsive switch and said second switch, the reaction between the rotor and stator upon the establishment of said operating circuit causing said rotor to rotate in one direction and said stator to rotate in the opposite direction against its bias to its second position, said control unit being moved by said rotor from its starting position toward a running position, said control unit closing said first switch as it moves from its starting position and then opening said second switch as it moves to an intermediate position to interrupt said first operating circuit for the control motor, operating means adapted to be moved in, a certain path by said stator as it moves between its first and second positions, an actuator for said safety switch controlled by said control unit, said control unit normally keeping said actuator out of the path of movement of said operating means but moving said actuator into said path as said control unit reaches its intermediate position, in-

terruption of said first operating circuit causing said stator to return to its first position under the influence of its bias of the control motor is deenergized at this time whereby said operating means engages said actuator and opens said safety switch, a second operating circuit for saidcontrol motor including a closed hot combustion switch, said last named circuit preventing deenergization of said control motor at the intermediate position of said control unit provided combustion is established before said control unit reaches its said intermediate position, a fixed stop, means associated with said control unit system, a control motor having a rotor and a stator, said 'stator being movable with respect said stator to move against said biasing means from said first to saidsecond position and to cause rotation of said rotor, means including said safety switch and the switching means positioned by-said rotor for causing energization of said electrical fuel controlling device, means including said switching means positioned by said rotor for interrupting the energizing circuit for said motor through the cold switch of the combustion responsive device and for establishing a new circuit to said motor through the hot switch of said combustion responsive device if combustion has occurred, and 'means for opening said safety switch by the movement of said stator to said first position if said hot switch is open at the time said energizing circuit is interrupted.

a 19. In a motor operated fuel burner controlsystem, a control motor having a rotor and a engaging said fixed stop to stall said control mo-;,

tor when said control unit reaches its running position, a return switch, a latch therefor, actuating means associated with said stop and .latch, said actuating means being in the path of stator, said stator being-movable with respect to said rotor between first and second positions upon energization of said motor, means biasing said stator to said first position, a switch actuated by said stator when moved to said second position, an electrically operated fuel feeding device for a burner, ignition means 'for said burner, means positioned by. said rotor for controlling the energization of said fuel feedin said operating means whereby it said control Y motor is deenergized said operating means will engage said actuating means which will remove said fixed stop and latch said return switch and reenergize said control motor, and means operated by said control unit for moving said actuating means out of the path of said operating means and tripping said latch when said control unit reaches its starting position.

17. In a motor operated fuel, burner control system, a control motor having a rotor and a stator, said stator being movable withrespect to said rotor between first and second positions upon energization of said motor, means biasing said stator .to its first position, switching means positioned by said rotor when the motor is energized, an electrical device which when energized causes the delivery of fuel to a burner, a safety switch, a main; controller, means including said main controller for initiating energization of said control motor to cause said stator'to move against said biasing means from said first to said second position and to cause rotation of said rotor, means including said safety switch and the switching means positioned by said rotor ior causing energlzation 01' said electrical-fuel zcontrolling device, and means positioned by the movement or said stator to said first position up'on deenergization oi said motor within a predetermined range or the rotation of said rotor to open said safety switch.

. 18. In a motor operated fuel burner control device and said ignition means, means for controlling the energization of said control motor including a main controlling switch having two pairs of sequentially engaging contacts, an' initial energizing circuit for said control motor including both of said pairs of contacts, and a maintaining circuit for said control motor including only the first to be engaged of said sets of contacts and said switch actuated by said stator.

20. In a control system, a control motor hav- I ing a rotor capable of continuous rotation and a stator, said stator being substantially instantly movable with respect to said rotor between first and second positions upon energization of said motor, stops to confine said stator to movement between said first and second positions, means biasing said stator to said'flrst position, a switch actuated by said stator when movedto said secondposition, a reduction gear train, a driven member in place thereof positioned by said rotor through, said gear train, means for controlling the energization of said control motor including a main controlling switch having two pairs of sequentially engaging contacts, an initial energizing circuit for said control motor inclu both or said pairs of contacts, and a maintaining circuit for said control motor including only the first to be engaged of said sets of contacts and said switch'actuated by said stator.

JOHN 'M. Wilson.

CERTIFICATE OF CORRECTION. Patent No. 2,577,555. June 5, 19L 5.

JOHN M. WILSON,

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column, line 7, for "unti" read --unit--; page 9, first column, line 27 "of" after "bias" read -if-; and second column, line 65; strike out the words in place thereof" and that the said Letters Patent should he read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 2nd day of October, A. D. 19LL5.

Leslie Frazer Seal) First Assistant Commissioner of Patents 0 CERTIFI GATE 0F CORRECTION Patent No. 2,577,555. June 1915.

7 JOHN M. wILsoN.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column, line 7, for "unti" read -unit--; page 9, first column, line 27 f r "of" after "bias" read --if-; and second column, line 65; strike out the words in place thereof" and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 2nd day of October, A. D. 19h

Leslie Frazer First Assistant Commissioner of Patents 

